Interpolating programmable gain attenuator

Abstract

A programmable gain attenuator includes a termination resistor. A first termination switch connects one side of the termination resistor to a first output. A second termination switch connects another side of the termination resistor to a second output. A first resistor ladder is arranged between a first input and the first side of the termination resistor. A first plurality of switches connect a corresponding tap from the first resistor ladder to the first output. A second resistor ladder is arranged between a second input and the second side of the termination resistor. A second plurality of switches connect a corresponding tap from the second resistor ladder to the second output. A first switch of the first plurality of switches is turned on, followed by a second switch of first plurality of switches turned off, followed by a third switch of first plurality of switches turned on. A first switch of the second plurality of switches is turned on, followed by a second switch of second plurality of switches turned off, followed by a third switch of second plurality of switches turned on.

1. A single-ended programmable gain attenuator comprising:
 a resistive ladder; 
 a plurality of switches corresponding to the resistive ladder and connected in a matrix to interpolate a desired voltage at the output, and connected to corresponding taps of the resistive ladder and to an output, said plurality of switches arranged in two or more rows and two or more columns, wherein the switches in each particular column of the matrix are arranged in parallel with the other switches in the particular column, having their respective inputs directly coupled together, and their respective outputs directly coupled together; and 
 a termination resistor. 
 
   
   
     2. A single-ended programmable gain attenuator comprising:
 a termination resistor; 
 a termination switch connecting one side of the termination resistor to an output; 
 a resistor ladder arranged between an input and the one side of the termination resistor; and 
 a plurality of switches each connecting a corresponding tap from the resistor ladder to the output, 
 wherein the switches are connected in a matrix having two or more rows and two or more columns, wherein the switches in each particular column of the matrix are arranged in parallel with the other switches in the particular column, having their respective inputs directly coupled together, and their respective outputs directly coupled together, and 
 wherein some of the switches of the first plurality of switches are turned on for interpolation. 
 
   
   
     3. The programmable gain attenuator of  claim 2 , wherein the matrix includes a fine matrix and a coarse matrix, which are controlled using fine and coarse selection logic, respectively, through a multiplexer. 
   
   
     4. The programmable gain attenuator of  claim 2 , wherein the switches are controlled so as to form a submatrix with some of the switches in the submatrix on, and other switches off. 
   
   
     5. A single-ended programmable gain attenuator comprising:
 a resistive ladder; 
 a plurality of switches corresponding to the resistive ladder and connected to interpolate a desired voltage at the output, and connected to corresponding taps of the resistive ladders and to an output;
 a termination resistor; 
 a fine selection logic for selection fine control switches out of the plurality of switches; 
 
 a coarse selection logic for selection fine control switches out of the plurality of switches; and 
 a multiplexer for passing control signals from the fine and coarse selection logic to the plurality of switches, 
 wherein the switches are arranged in a matrix having two or more rows and two or more columns, wherein the switches in each particular column of the matrix are arranged in parallel with the other switches in the particular column, having their respective inputs directly coupled together, and their respective outputs directly coupled together. 
 
   
   
     6. A programmable gain attenuator comprising:
 a termination resistor; 
 a first termination switch connecting one side of the termination resistor to a first output; 
 a second termination switch connecting another side of the termination resistor to a second output; 
 a first resistor ladder arranged between a first input and the first side of the termination resistor; 
 a first plurality of switches each connecting a corresponding tap from the first resistor ladder to the first output, wherein the first plurality of switches are connected in a first matrix having two or more rows and two or more columns, wherein the switches in each particular column of the first matrix are arranged in parallel with the other switches in the particular column, having their respective inputs directly coupled together, and their respective outputs directly coupled together; 
 a second resistor ladder arranged between a second input and the second side of the termination resistor; and 
 a second plurality of switches each connecting a corresponding tap from the second resistor ladder to the second output, wherein the second plurality of switches are connected in a second matrix having two or more rows and two or more columns, wherein the switches in each particular column of the second matrix are arranged in parallel with the other switches in the particular column, having their respective inputs directly coupled together, and their respective outputs directly coupled together, 
 wherein some of the switches of the first plurality of switches are turned on for interpolation, and 
 wherein some of the switches of the second plurality of switches are turned on for interpolation. 
 
   
   
     7. The programmable gain attenuator of  claim 6 , wherein the first and second matrices each includes a fine matrix and a coarse matrix, which are controlled using fine and coarse selection logic, respectively, through a multiplexer. 
   
   
     8. The programmable gain attenuator of  claim 6 , wherein the switches in each of the first and second matrices are controlled so as to form corresponding submatrices with some of the switches in each submatrix on, and other switches off. 
   
   
     9. The programmable gain attenuator of  claim 6 , further including a plurality of resistors connected between the corresponding taps of the first and second resistor ladders.